A method for scrambling a digitally transmitted television signal

Claim 2

The method of claim 1, characterized in that a predetermined number of consecutive video data packets of a television image are transmitted non-scrambled and the rest of the video data packets of the television image are scrambled.

Claim 3

The method of claim 1, characterized in that randomly selected video data packets of a television image are transmitted scrambled and the rest of the video data packets of the television image are transmitted non-scrambled.

Claim 4

The method of claim 1, characterized in that a television image sequence is scrambled by scrambling the video data packets of predetermined television images.

Claim 5

The method of claim 4, characterized in that a television image sequence is scrambled by scrambling at least some of the video data packets of the intracoded images.

Claim 6

The method of claim 1, characterized in that a television image sequence is scrambled by scrambling predetermined video data packets of predetermined television images.

Claim 7

The method of claim 1, characterized in that a television image sequence is scrambled by randomly scrambling video data packets of randomly selected television images.

Claim 8

The method of claim 1, characterized in that the video data packets related to predetermined parts of a television image are transmitted non-scrambled.

Claim 12

A television transmitter comprising in parallel branches encoding means (1, 2, 3) for a video, audio, and data signal and packetizing means (4) to transmit each of the signals in data packets, with all branches combined by a multiplexer (6) and with the video data packets, audio data packets, and other data packets brought to the separate inputs of said multiplexer the combined output of which will yield a packet-form digital television image signal containing packets related to at least two different program transmissions, characterized in that each branch includes after the packetizing means (4) packet scrambling means (5) operative to scramble some of the packets related to a particular program, and not to scramble the remaining packets related to that program.

Claim 13

The television transmitter of claim 12, characterized in that the packet scrambling means (5) comprise a scrambling block (23) for the reception and scrambling of a packet, a scrambling decision and selection block (21) for the reception of a packet, connected in parallel to the input of the scrambling block (23), in which a decision is made about the scrambling of a packet and information about the decision is then taken to the packet scrambling block (23), and an encryption key set (22) containing information about the packets to be scrambled and the scrambling method, which informs the scrambling decision and selection block (21) about the packets to be scrambled and gives the encryption keys to the scrambling block (23).

Claim 14

A television receiver for the reception of digital television image signal transmitted in packet form, comprising a demultiplexer (12) to separate video packets, audio packets, and other data packets from packetized television image signal to respective branches, each of which comprises depacketizing means (14) and decoding means (15, 16, 17) for video, audio, and data signals, characterized in that there are in each branch before the depacketizing means (14) descrambling means (13) for identifying packets related to a particular program and for identifying the scrambled and non-scrambled packets related to the same transmission of the same program and for descrambling only the crambled packets.

Claim 15

The receiver of claim 14, characterized in that the descrambling means (13) comprise a descrambling block (33) for the reception and descrambling of a packet, a decryption key set (32) comprising the decryption keys with which the descrambling block (33) descrambles a scrambled packet, and a packet identification block (31) connected in parallel to the input of the descrambling block (33), which identifies the location of a packet and determines on the basis of the location and the decryption key read from the decryption key set (32), whether a received packet is scrambled or not, and sends that identification information to the descrambling block (33).